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The system clock is powered by a small battery on the motherboard. If this battery is working, the clock should stay set, with the Windows operating system adjusting the time as needed for Daylight Savings Time when connected to the Internet. However, if you've found yourself needing to reset your computer clock every time the system reboots, the complementary metal oxide semiconductor (CMOS) battery has likely failed. The failure may or may not accompany a message at boot time stating that the time and date is not set. Your computer’s user manual or the manufacturer’s website will tell you which type of battery you need.

1.

Shut the computer down and unplug its power cable.

2.

Press and hold the power button for a few seconds to discharge any remaining electricity from the motherboard.

3.

Remove the computer’s side panel. Depending on model, the panel may be held in place with Phillips screws, or it may have a latch.

4.

Lay the computer on its side on a flat surface.

5.

Touch an unpainted metal surface on the computer case to ground yourself.

6.

Find the CMOS battery, which is a silver, coin-cell battery. It’s usually held in place with a clamp.

7.

Carefully remove the battery. You may need to press a latch in the clamp in order to release it.

8.

Install the new battery, making sure the polarity is correct.

9.

Replace the computer panel, and plug the power cable back in.

10.

Turn your system on, and enter BIOS. The key you need to press to enter BIOS varies for different models, but common ones are the “Delete” or “Esc” key, or a function key. If Windows loads, you’ve waited too long and must reboot.

11.

Use your arrow keys to change the time and date in BIOS.

12.

Save your changes and reboot.

Things Needed

Replacement CMOS battery

Phillips screwdriver

Tips

You can purchase CMOS batteries from any store that sells watch batteries.

CMOS batteries should last several years. If your computer is still under warranty when your CMOS battery dies, you may be entitled to a free replacement from the manufacturer. Consult your user manual or computer manufacturer’s website for more information.

Warning

Do not lay your computer on a carpet before working inside it. The motherboard is very sensitive, and any amount of static electricity may damage it.

References (2)

About the Author

A writer and proofreader since 2006, B. Steele also works as an IT Help Desk analyst, specializing in consumer and business user tech support. She earned a B.A. in English and journalism from Roger Williams University. Steele also holds certifications as a Microsoft-certified desktop support technician, Microsoft-certified IT professional, Windows 7 enterprise support technician and CompTIA A+ IT technician.